Use of devices for hydraulic conveyance of loose materials is aimed at the solution of a basic problem, viz., to prevent the particles being conveyed from contact with the moving and flow-through components of pressure units, which leads to abrasive wear of said components, as well as to substitute low-pressure suction dredges or dredger pumps by much more powerful water pumps.
Hydraulic conveyance of loose materials over long distances requires, as a rule, intermediate pumpingover stations. However, such stations can be successfully substituted by a group of hydraulic conveying devices operating alternatively and accompanied, whenever necessary, by a parallel operation of several water pumps serving one such device.
Thus, the distance over which loose materials can be conveyed with the use of one such device depends, first and foremost, on the strength characteristics of said device.
Moreover, such device should meet a number of requirements determined by the specificity of their operation and influencing reliability and economy of the latter. One of the most important requirements resides in a reliable operation of such devices ruling out clogging or hanging of the solid material being handled in the chamber of the device, which depends on the method and direction of discharge accounted for by the arrangement of the discharge pipes of the device.
Thus, dredger pumps are able to transfer the whole amount of the loose material being handled having a definite comparably uniform density of the slurry, whereas various constructions of the aforesaid devices are as a rule featured by the presence of the so-called "dead" zones, i.e., a certain amount of the loose material that remains in the chamber after discharging, or the presence of a constant amount of process water in the chamber when the latter is filled with the loose material but incompletely. In this case when loose material different in quality and composition is fed into the chamber during the process cycle, discharge of the material will also be carried out differentially without averaging the material being handled, which affects adversely stability of operation of the device.
One state-of-the-art plant for hydraulic conveynace of slimes is known (SU, A, 252,208) to comprise a group of spherical chambers, each being provided with a pressure liquid flow feeding pipe, a liquid discharge pipe, a loose material charging pipe, and a slurry discharge pipe, each of said pipes communicating with the respective pipeline. The pressure liquid flow feeding pipe and the liquid discharge pipe are located in the top portion of the chamber, while two other pipes, in the bottom portion of the chamber, a flexible diaphragm being interposed therebetween, which is adapted to discharge excess liquid when the chamber is being filled and to expel the slurry under pressure into the respective pipeline.
A spherical shape of the chambers of the aforedescribed plant makes provision for uniform distribution of stresses in the walls during operation under pressure. However, provision of four holes for holding the aforesaid pipes thereto and two another holes for the flanged-mounted flexible diaphragm affects much the safety margin of the chambers. Provision of a flexible diaphragm in the chamber places limitation upon the pressure of the discharge liquid flow due to low strength characteristics of said diaphragm, which in turn reduces the slurry conveyance range. Technological capabilities for making high-capacity spherical chambers are limited very much, which results in a great number of switching-over operations and hence in a bad concentration of local stresses at places where the pipes, as well as the diaphragm are held.
Location of the loose material feeding pipe and the slurry discharging pipe in the bottom portion of the chamber predetermines charging a loose material in the zone of countercurrent, which involves additional head losses and hence additional power consumption, and its discharge from the chamber in a downward current, which promotes clogging of said pipes.
The operating efficiency of the plant as a whole is affected due to the presence of the "dead" zones in the upper portions of the chambers, which are filled with liquid after the loose material has been charged therein.
One more prior-art device for hydraulic conveyance of loose materials (SU, A, 912,612) is known to comprise a vertical chamber having a cylindrical side surface, a cover and a bottom and provided with a pipe for feeding a pressure liquid flow, which is then discharged from the chamber when the loose material being handled is charged into said chamber, a loose material charging pipe and a pipe for discharging the slurry in an upward flow, which is arranged coaxially with said loose material charging pipe and is accommodated therein, both of said pipes being arranged coaxially with the longitudinal chamber axis and being fixed to the chamber cover, while some portions thereof are located inside said chamber.
In the aforedescribed device the pressure liquid flow feeding pipe and the liquid discharging pipe are integrated into a single pipe operating alternatively. Besides, the chamber is provided with a by-pass pipe aimed at prevention of a "dead" zone from the loose material in the chamber bottom portion, as well as with an elastic bulb secured in the chamber cover and adapted to transfer the delivery pressure in the course of discharging the slurry from the chamber.
The aforementioned shape of the chamber is featured by but a low margin of safety. Provision of two holes for attaching the pipes and another two holes for fastening the bypass pipe also affects adversely the strength characteristics of the chamber and hence reduce the range of the slurry conveyance. Provision of an elastic bulb also place limitation on the delivery pressure developed and hence the range of the slurry conveyance. Besides, said bulb is liable to be sucked into the slurry upward flow discharging pipe. Apart from that, provision of such a bulb predetermines the presence of a "dead" zone of another kind in the chamber, that is, a constant volume of process water, which curtails the chamber discharge time and hence results in a great number of switching-over operations, which in turn affects adversely the chamber strength characteristics. Provision of said bulb is also causative of a low density of the slurry being conveyed, which is accounted for by the construction of the dredger pump, and a drastic change of the density in the course of the operating cycle.
The device under consideration is also featured by a sophisticated production process, assembly and mounting, which renders its application less efficient, as well as by possible nonuniformity of charging the loose material being handled, which tells adversely on the quality of the slurry.